[Bug debug/100960] var-tracking: parameter location in subregister not tracked

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100960

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Slightly related was
https://gcc.gnu.org/legacy-ml/gcc-patches/2010-03/msg01379.html
So, perhaps for the case where we do not track the source register in the wider
mode we could for var-tracking purpose also pretend the move is not a DImode
copy, but a SImode copy.
But what I wrote above is also an option, record permanent equivalency that the
narrower value is lowpart subreg of the wider value.